The present invention relates to a specimen supporting device and more in particular to a specimen supporting device suitable for supporting a specimen within a vacuum chamber.
In an ion implanting apparatus known as a semiconductor fabricating device, a multiplicity of wafer targets are provided as specimens in an implanting chamber, and are implanted with ions while being sequentially relocated to predetermined positions. In view of the fact that the implanting chamber is required to be kept in vacuum, vacuum attracting means known as specimen holding or supporting means in the atmosphere cannot be used as specimen supporting means in the implanting chamber. For this reason, screwing means is generally used for supporting specimens in the implanting chamber. The problems of the screwing means are that it is difficult to fix specimens of different sizes on the one hand and the specimens are liable to be broken on the other hand.
A solution of these problems have been proposed by means of applying a voltage between a specimen and a specimen-attracting portion made of insulating member whereby the resulting electrostatic atractive force is used to support the specimen by attraction to the specimen attracting portion, as disclosed for example in U.S. Pat. No. 3,983,401 for supporting and securing target wafers for exposure to an electron pattern in electron projection systems. In order to obtain an attractive force equivalent to that of vacuum attraction (1 kg/cm.sup.2 or a pressure almost equal to the atmospheric pressure) in this system, the specimen attracting portion is required to be made up of an insulating material several .mu.m thick and having a breakdown voltage of more than 10.sup.5 V/cm.
Although mica or Si0.sub.2 may be used as the insulating material of the specimen attracting portion, it is practically very difficult to produce a mica or Si0.sub.2 film of a fixed thickness of about several .mu.m. This problem is soluble by thickening the film. Nevertheless, such a solution requires an increased applied voltage.